4K DCP problems

[scorpio81]

Hi!
Tried to encode 4K DCP with 2.12.8 and 2.13.36 versions. Encoding passed without any problems and DCP ingested ok. But problems came out when I tried to play it. Playing my DCP being alone in the playlist was fine. But if there were preceding DCPs then DCP2000 server failed to start my DCP, there were green flashes on the screen and then playback freezed. Transition from my 4K DCP to other DCPs was accompanied by a single green flash on the screen but next DCP started fine.
So I believe something went wrong with the 4K encoding in the 2.12.x and later versions because the same source video 4K-encoded with the same encoding settings with 2.10.9 version played perfectly.

P.S. Transitions were between 4K DCPs encoded with 2.10.9 and 2.12.8 (2.13.36). I'll try transitions between DCPs encoded only with 2.12.8 (2.13.36) and transitions from 4K DCP encoded with 2.12.8 (2.13.36) and 2K DCPs encoded with 2.10.9. Will report in the following post ASAP.

[scorpio81]

Alright, all other possible transitions are fine. So the problem is with 4K DCPs encoded with different versions of DOM.
As it is written in the list of changes, the resolution levels with 4K outputs have been fixed between versions 2.10.x and 2.12.x. Maybe this is the reason for some servers going nuts switching from one data structure to another.
If one has 4K DCPs encoded with versions prior to 2.12.x then I would advise either to encode new 4K DCPs with older versions of DOM or to completely re-encode old 4K DCPs with the latest version. Otherwise test transitions between DCPs on your server prior to creating playlists.

[Carsten]

Good hint. 4k J2k had a code correction on 2.11.23, and it may indeed be that switching between old and new 4k codestreams causes issues on some servers. I know that the Doremis have demonstrated to be picky about 4k anyway.

https://dcpomatic.com/mantis/view.php?id=1125

It's not likely to happen often, but, as you proved, it is not impossible to hit you. Re-Encoding from the original media, or re-encoding the 'bad' 4k DCP with at least 2.11.34 or later should solve the problem. Another short-term option could be to put short 2k blacks between these parts?

- Carsten

[scorpio81]

Carsten, yes, 2k blacks will help. In my case, I still have the originals so I will re-encode them with the latest DOM release.

[scorpio81]

Re-encoding "bad" DCP doesn't work. DOM passes frames encoded in older versions unaltered.
I have made a mixed DCP: the first part was an original video file and the second part was a j2c-file encoded in 2.10.9. So an original file was encoded and a j2c-file was not re-encoded thus resulting in a green flash on the screen between these two parts.

[Carsten]

You need to adjust a minor image parameter to force re-encoding.E.g. crop away one line, or add an invisible burn-in subtitle. Maybe at some time Carl will add a checkbox to force full encode.

- Carsten

[Mario B]

4K DCP VF Added Subtitles Out of Sync

Hi Carl,
I have an issue I hope you may help me.

I need to add spanish subtitles to an existing 4K OV DCP that is going to be played in a 2K projector in the movie theater.

Ive already created a VF as I usually do but in the theater the subtitles always come out of sync.

Is there a way to create a VF in order to achieve the projection, or I just have to make a new DCP in DOM in 2K format?

Mario

[Carsten]

Which version of DCP-o-matic do you use, and did you check that DCP in DCP-o-matic player for sync issues?


- Carsten

[Mario B]

I think I was using 2.12.2 but then I realized that... and proceed to download last stable release 2.12.9 and still continue the trouble.

Yes, I checked in the dcp player and the subtitles were in sync, everything was fine. That why I send the files to the theater, but they report back that the subtitles continue out of sync.

[Carsten]

That is weird - do you have more information about that DCP aside from 4k? Frame rate, IOP/SMPTE, etc.? Server/projector type? If the OV plays okay, and a VF containing only timed text is out of sync in the subs - that is very weird...

- Carsten